Screen for paper making



Patented July 3, 1928.

UNITED STATES 1,675,612 PATENT OFFICE.

ISAAC LAUREN LAIRD, OF SOTITH WALPOLE, MASSACHUSETTS, ASSIGNOR T BIRD MACHINE COMPANY, OF SOUTH WALPOLE, MASSACHUSETTS, A CORPORATION OI MASSACHUSETTS.

Application filed July 22,

This invention relates to screens for use primarily in paper making, and is designed more particularly for the coarse screening of material suspended in a liquid. For the purpose of this explanation of its construction and operation, it maybe considered as a knotter or coarse screen for removing the knots, slivers, and larger particles from wood p p The present invention has for its objects the provision of more eflicient means for screening, and to improve upon knotters and screens in present use.

An embodiment of the invention is illus- 1 trated in the annexed drawings, wherein- Fig. 1 is a vertical cross-section of the device, with various parts in elevation, suchas the pulley, central shaft, and shower P p Fig. 2 is a top plan view of the device. Referring to the drawings, the machine consists of a casing 2, made, for example, of sheet metal of suitable thickness supported by uprights 4 and a lower spider 6. 25 The lower spider may, as here, have three arms each of which is bolted to an upright 4. -This lower spider carries a step or thrust bearing 8 which serves to center and carry a rotating shaft 10. The uprl hts 4 30 are connected at their upper ends by t e upper spider 12 which also has three arms and contains the upper bearing 14 which serves to center the shaft and hold itin position for rotation. To the upper spider is attached by suitable means a stock inlet 16 which rests at its outer end upon the casing 2 and the angle 18 used to stiffen the casing. A drive pulley 20 is keyed or otherwise fastened to the shaft 10 so as to drive the same when the pulley is rotated. There is also affixed to the shaft 10 a distributing bowl 22 which is carried by and rotates with the shaft. A shower pipe 24 extends into the screen 25 from a point adjacent the'bowl 22. This shower pipe is provided with suitable nozzles 26 and is fed through the gooseneck 28 and feed pipe 30 which is attached to one of the arms of the spider 12 as shown in the drawings. In addition to the nozzles 26 the shower pipe 24 may be provided with holes 32 for the purpose of projecting jets of water against the screen. I I n The screen 25 consists of lates of perforated sheet metal (indicated in the drawings as screen) suitably fastened together so SCREEN ron rarer. MAKING.

1927. serial 110. 207,042.

as to form an inverted truncated cone (the fastenlngs and joints of the plates in the screen-not being shown) which is held and rotated as to turn withthe distributing bowl 22 and other rotating parts of the screen. At the top of the screen is aflixed a stock guide34 which deflects downwardly the'stock received from the distributing bowl 22. The taillng guide 36 is supported and rotated by the shaft 10 through the medium of a tailing distributing bowl 38 which is keyed directly to the shaft 10. The tailing distributin bowl has wing or spiderlike arms 40 whic brace and hold the screen 25 as can be seen from Fig. 1 of the drawing, A shower pipe 42, placed parallel with the outside of the screen, contains a series of holes 44-adapted to project water against the screen. This shower pipe is supported by a bracket-46 and is fed through the elbow 48- In the operation of the device, the shaft and all the units attached thereto are rotated at the proper speed which depends largely upon the nature of the wood pulp or material to be screened or knotted. This speed can readily be ascertained by experiment and as a'practical matter the maximum speed is limited only by the tendency of the particles to felt or met on the inside of the rotating screen. The stock to ,be screened enters through the inlet 16 and passes downwardly into the distributin bowl 22. After the bowl is sufficiently filled, centrifugal force throws off an evenly distributed sheet of stock from thepriphery of the bowl. This sheet of stock strikes the stock guide 34 which is rotated by the screen. The guide 34 prevents the stock from splashing or escapmg and guides it downwardly along the screen. Centrifugal force causes acceptable stock to pass through the perforations 1n the screen. A surplus of stock, with-the help of the outside and inside showers, carries the knots and slivers downwardly and when they reach the tailing guide 36, only a comparatively small amount of good fibre is left. Tail m shower nozzles 26 wash the knots and sivers and the remaining ood fibre down the slope of the tailing guide 36 to- 105 ward and into its center openlng where they drop through and into the tailing distributing bowl 38. The proper dilution of the mlxtureof knots, slivers and good fibres thus obtained obviates the necessity of .an addi- 110 tional inside shower at this point, the outside shower 42 bein sufiicient, because of the decreased centri ugal force due to the smaller circumference of the cone at this section, and hence a. lower rate of lineal speed. Theoutside shower alone gives satisfactory operation in many cases. The

good fibre or accepted stock pass through the perforations in the screen and fall to the bottom of the casing from which it flows out through a discharge opening 50.

The outside shower with the aid of gravity forces the knots and slivers to drop throng the openings between the arms of the tail ng distributing bowl 38, through the opening in the floor of the casing 2 and thence out between the arms of the bottom spider 6.

In my use of the word stock. in the following claims, I am using it mean unscreened material suspended in a hquid, whether or not such material is strictly paper stock 'or paper making material, and the word tailings to mean simply coarser ma- -of a substantially frusto-eonical section terial in said stock.

Having described my invent1on,' what I wish to claim and-secure by Letters Patent 1. In a centrifugal machine of the class described, having, in combinat10n, a screen adapted to be rotated about an axis, means .to distribute stock about the inside of the of the screen near one end, a shower adapted to clear cloggedapertures in said screen means to collect unscreened material an distribute it about the insideof a. lower screening section, whereby said material is subjected to a second screening operation,

and means to se arately conduct the accepted stock and ta11i from the screen.

3. A machine of e class described, having, in combination, a centrifugal screen adapted to be rotated abouts-substantially vertical, axis, means to uniformly distribute stock aboutthe inside of the screen near its upper end, a shower adapted to clear clogge apertures in said screen, means to collect unscreened material and distribute it about the inside of a lower screening section, whereby said material is subjected to a second screening operation, and means to conduct the accepted stock and tailings from the screen;

4. A machine of the class described, having, in combination, a screen member having as its screen surface a surface of revolu tion, means to distribute stock about the inside ofthe screen .near one end of the same, a shower. adapted to clear the apertures in said screen, means to collect the unscreened material and distribute said material about the inside of a lower screening section, whereby said material is subjecte to a further screening operation, and means toseparately conduct the accepted stock and tailings from the screen.

'5. A machine, of the class described,-hav

ing, in combination, a screen member having as its screen surface a surface of revolu-' tion, means-to -distri'bute stock about the inside of the screen near one end of the same, a shower adapted to clear theiapertures in said screen. and direct the tailings downwardly, means to collect the unscreened material and distribute said material about the inside of a lower screening section, whereby said material is subjected to a further screening operation, and means to separately conduct the accepted stock and tailings from the screem i 6. A machine of the class described, having, in combination, a screen member adapted to be revolved about a substantially vertical axis, having as its screen surface. a surface of revolution, means to distribute stock about the inside of the screen near the upper end of the same, means to collect the unscreened material and distribute said ma- .terial about the inside of a lower 'ortion of said screen member, whereby sai material is subjected to' a further screening operation, and means to separately conduct the accepted stock and tailings from the screen.

7. A machine of the class described, having, in combination, a screen member adapted to be revolved about a substantially vertical axis, revolving means to distribute the stock about the inside of the screen near the upper end of'the same, and means to separately conduct the accepted stock and tailings from the screen.

8. A machine of the class described, having, in combination, a screen member adapted to be revolved about a substantially vertical axis, means to distribute the stock in a sheet about the inside of the screen near the upper end of the. same, and means for separately conducting the accepted stock and tailings from the screen.

9.;A machine of the class described, having, in combination, a screen member adapted to be revolved about a substantially vertical axis, and stock distributing bowl adapted to be revolvedabout the same axis so as to-distribute stock about the inside of the near the upper end of the same, and means to separate y conduct the accepted stock and tailings from the screen.

. a shower adapted to 1Q. A machine of the class described, 'having, in combination, a screen member adaptedto be revolved about a substantially vertical axis, and -stock distributing bowl adapted to be revolved about the same axis so as to distribute stock about the inside of the screen near the upper-end of the same, clear the apertures in said screen, and means to separately conduct the accepted stock and tailings from the screen.. v 1

1 1. A machine of the class described, having, in combination, a screen member adapted to be revolved about a substantially vertical axis, means to distribute stock about the inside of the screen near the upper end of the same means to collect the unscreened .material and uniformly distribute said material about the inside of a lower screening section, whereby said material is subjected to a further screening operation, and means to separatel conduct the accepted stock and tallings rom the screen.

12. A machine of the class described, having, in combination, a screen member having as its screen surface a surface ofrevolution, means to revolve said screen member about its axis, means to conduct stock to the screen, means to direct the entering stock along the inside of the screen, means to clear clogged apertures in said screen member, means to collect the unscreened material and distribute the same in a diluted conditionabout the inside of a second screening section, whereby said material is subjected to a further screening operation, and means to se arately conduct the. accepted stock and tai ings from the screen.

13. A machine of the class described, having, in combination, a screen member having as its screen surface a surface of revolution,

means to revolve'said screen member about itsaxis, means to conduct, stock to the screen, an imperforate stock guide to direct the entering stock along the inside of the screen means to clear clogged apertures in said screen member, means to collect the unscreened material and distribute the same in a diluted condition about the inside of a second screening section, whereby said material is subjected to a further screening operation, and means to separately conduct the accepted stock and tailings from the screen.

14. A machine pf the class described, having, in combination, a screen member having as its screen surface a surface means to revolve said screen member about its axis, means to conduct stock to the screen, means carried by said revolving screen member. to direct the entering stock along the inside of the screen, means to clear-clogged apertures in said screen member, means to collect the unscreened material and distribute the same in a diluted condition about the inside of a second screening section, whereby said material is subjected to a further screening operation, and means to separately conduct the accepted stock and tailings from the screen. V

15. A machine of the class described, having, in combination, a screen member having as its screen surface a surface of revolution, means to revolve said screen member about its axis, means to conduct stock to the screen, an imperforate stock guide, carried by said screen member, adapted to direct the entering stock alon means to clear clogged apertures in said screen member, means to collect the unof revolution,

g the inside of the screen,

screened material and distribute the same in a diluted condition about the inside of a .second screening section,

whereby, said mafurther screening separately conduct tailings from the ISAAC LAUREN LAIRD.

terial is subjected to a operation, and means to the accepted stock and screen. 

